Shock-absorbing joint for interconnecting front and rear wheel-carrying frame members of a bicycle

ABSTRACT

A shock-absorbing joint includes a tubular casing connected securely to the front wheel-carrying frame member of a bicycle, and confining an accommodating space with a central axis that is disposed horizontally and that extends in a transverse direction relative to a riding direction of the bicycle. A coupling shaft is disposed in the accommodating space, and extends along the central axis of the accommodating space. A spiral spring plate is disposed in the accommodating space, and has an innermost end connected to the coupling shaft and an outermost end connected to the tubular casing. The spiral spring plate is wound about the coupling shaft to form a series of interconnected turns of increasing radius. A connecting bracket is connected securely to a rear wheel-carrying frame member of the bicycle. The tubular casing is mounted rotatably on the connecting bracket, while the coupling shaft is mounted non-rotatably on the connecting bracket.

FIELD OF THE INVENTION

The invention relates to a shock-absorbing joint, more particularly to ashock-absorbing joint for interconnecting front and rear wheel-carryingframe members of a bicycle.

BACKGROUND OF THE INVENTION

A shock-absorbing joint for interconnecting front and rearwheel-carrying frame members of a bicycle is known in the art. The knownshock-absorbing joint generally includes a hydraulic (or pneumatic)cylinder (or piston) and a spring associated with the cylinder in orderto absorb the shock experienced by the bicycle when the latter is inuse. However, the following disadvantages result from the use of theknown shock-absorbing joint:

(1) In case the known shock-absorbing joint has a relatively longcylinder arm for connection with one of the front and rearwheel-carrying frame members, the cylinder arm can travel a longdistance so as to provide sufficient shock-absorbing effects. However,in order to achieve such effects, the spring employed therein mustpossess a relatively large spring force, thereby reducing theshock-absorbing effect.

(2) In case the known shock-absorbing joint has a relatively shortcylinder arm for connection with one of the front and rearwheel-carrying frame members, the distance that is traveled by thecylinder arm is very short, thereby consequently resulting in poorshock-absorbing effects.

SUMMARY OF THE INVENTION

Therefore, the main object of this invention is to provide ashock-absorbing joint for interconnecting front and rear wheel-carryingframe members of a bicycle and capable of providing excellentshock-absorbing effects.

Accordingly, the shock-absorbing joint of the present invention isadapted to interconnect a front wheel-carrying frame member and a rearwheel-carrying frame member of a bicycle, and includes a tubular casing,a coupling shaft, a spiral spring plate, and a connecting bracket. Thetubular casing is adapted to be connected securely to one of the frontand rear wheel-carrying frame members. The tubular casing confines anaccommodating space which defines a central axis that is disposedhorizontally and that extends in a transverse direction relative to ariding direction of the bicycle. The coupling shaft is disposed in theaccommodating space, and extends along the central axis of theaccommodating space. The spiral spring plate is disposed in theaccommodating space, and has an innermost end connected to the couplingshaft and an outermost end connected to the tubular casing. The spiralspring plate is wound about the coupling shaft to form a series ofinterconnected turns of increasing radius. The connecting bracket isadapted to be connected securely to the other one of the front and rearwheel-carrying frame members. The tubular casing is mounted rotatably onthe connecting bracket. The coupling shaft is mounted non-rotatably onthe connecting bracket.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of this invention will become moreapparent in the following detailed description of the preferredembodiment of this invention, with reference to the accompanyingdrawings, in which:

FIG. 1 is a fragmentary and partly sectional view of a shock-absorbingjoint of the present invention for interconnecting front and rearwheel-carrying frame members of a bicycle;

FIG. 2 is an exploded view of the shock-absorbing joint of the presentinvention;

FIG. 3 is an enlarged, fragmentary and cross-sectional view of theshock-absorbing joint of the present invention, illustrating how thefront and rear wheel-carrying frame members of the bicycle areinterconnected; and

FIG. 4 is another enlarged, fragmentary and cross-sectional view of theshock-absorbing joint of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1, 2 and 3, the preferred embodiment of ashock-absorbing joint according to the present invention is adapted tointerconnect a front wheel-carrying frame member 30 and a rearwheel-carrying frame member 40 of a bicycle 1. The preferred embodimentincludes a tubular casing 20, a coupling shaft 21, a spiral spring plate22, and a connecting bracket 50.

As illustrated, a tubular casing 20 is connected securely, such as bywelding, to the front wheel-carrying frame member 40 of the bicycle. Thetubular casing 20 includes a circumferential wall 23 which confines anaccommodating space 230 therewithin with a central axis that is disposedhorizontally and that extends in a transverse direction relative to ariding direction of the bicycle. The circumferential wall 23 has a stopmember 54 mounted on an outer surface thereof by the use of a screwfastener 237. Preferably, the stop member 54 is made from an elastomericmaterial.

The coupling shaft 21 is disposed in the accommodating space 230 of thecircumferential wall 23, and extends along the central axis of theaccommodating space 230.

The spiral spring plate 22 is disposed in the accommodating space 230 ofthe circumferential wall 23. The spiral spring plate 22 has an innermostend 220 connected to the coupling shaft 21, and an outermost end 221connected to the circumferential wall 23. The spiral spring plate 22 iswound about the coupling shaft 21 to form a series of interconnectedturns of increasing radius.

The connecting bracket 50 is connected securely to the frontwheel-carrying frame member 30 of the bicycle. The tubular casing 23 ismounted rotatably on the connecting bracket 50. The coupling shaft 21 ismounted non-rotatably on the connecting bracket 50.

As shown in FIG. 3, the spiral spring plate 22 is formed by bendingcontinuously an elongated metal plate into the series of interconnectedturns with the increasing radius, thereby defining a plurality ofclearances between adjacent ones of the turns and between an innermostone of the turns and the coupling shaft 21.

A cushioning filler 24, made from an elastomeric material or foamedmaterial, is disposed in the circumferential wall 23, and fills theclearances that are defined by the spiral spring plate 22.

In the preferred embodiment, the connecting bracket 50 includes aconnecting plate 52 that extends longitudinally in the transversedirection and that has left and right ends 520, and left and rightsupport plates 51 that extend respectively and transversely from theleft and right ends 520 of the connecting plate 52 to flank oppositeends 234 of the circumferential wall 23. The connecting plate 52 isconnected securely, such as by welding, to the rear wheel-carrying framemember 40 (see FIG. 4). The left and right support plates 51 have theopposite ends 234 of the circumferential wall 23 mounted rotatablythereon, and further have opposite end portions 211 of the couplingshaft 21 mounted non-rotatably thereon.

Each of a pair of cap members 53 has an outer portion 530 that ismounted non-rotatably on a respective one of the left and right supportplates 51, and an inner portion 531 that extends into a respective oneof the opposite ends 234 of the circumferential wall 23. Preferably, theleft and right support plates 51 are formed with non-circular openings511, such as hexagonal openings, therethrough. The outerportion 530 ofeach of the cap members 53 has a cross-section that complements theopenings 511 in the respective one of the left and right support plates51 to enable non-rotatable engagement of the cap members 51 with theleft and right support plates 51 in the openings 511.

A pair of bearing members 55 couple rotatably and respectively theopposite ends 234 of the circumferential wall 23 and the inner portions531 of the cap members 53. Preferably, the opposite ends 234 of thecircumferential wall 23 are provided with two bearing-retention rings235 in order to mount the bearings members 55 therein. Each of theopposite end portions 211 of the coupling shaft 21 is formed with anon-circular cross-section, such as rectangular, along a planetransverse to the central axis. The inner portion 531 of each of the capmembers 53 is formed with a socket that engages non-rotatably arespective one of the end portions 211 of the coupling shaft 21.Preferably, each of the end portions 211 of the coupling shaft 21 isformed with an internally threaded axial bore 212 such that a screwfastener 532 extends through a respective one of the cap members 53 andengages the axial bore 212 in a respective one of the end portions 211of the coupling shaft 21.

In this preferred embodiment, one of the abutment edges 521 of theconnecting plate 52 is formed with a notch 522 that is registered withthe stop member 54. The outermost end 221 of the spiral spring plate 22is formed with a threaded hole 222 therethrough. The circumferentialwall 23 is formed with a plate-retention recess 239 and a radial hole232 that communicates the accommodating space 230 with an exteriorthereof and that is aligned with the threaded hole 222 in the spiralspring plate 22. A fastener plate 231 is disposed in the plate-retentionrecess 239 in such a manner that a portion thereof projects radially andoutwardly from the circumferential wall 23. A screw fastener 233 isextended through a hole in the fastener plate 231 and the radial hole232 in the circumferential wall 23 to engage the threaded hole 222 inthe spiral spring plate 22, thereby connecting securely the outermostend 221 of the spiral spring plate 22 to the circumferential wall 23.The fastener plate 231 has two opposite edges provided with a pair ofcushioning bumpers 238, respectively. Each of the cushioning bumpers 238is rotatable with the circumferential wall 23 relative to the connectingbracket 50. One of the cushioning bumper 238 is capable of abuttingagainst one of the abutment edges 521 of the connecting plate 231 tolimit rotation of the circumferential wall 23 relative to the connectingbracket 50 in the certain direction. Preferably, the cushioning bumpers238 are made of an elastomeric material. The coupling shaft 21 is formedwith an axially extending slot 213 for engaging securely the innermostend 220 of the spiral spring plate 22. Alternatively, the innermost end220 of the spiral spring plate 22 can be integrally formed with thecoupling shaft 21 in order to achieve firm engagement therebetween.

As best shown in FIG. 1, in case the circumferential wall 23 is turnedabout the central axis in the anti-clockwise direction due to acollision action or braking operation so as to bring the spiral springplate 22 to wind about the coupling shaft 21 in the same direction, thecushioning bumper 238 will abut against one of the abutment edges 521 ofthe connecting plate 52 to result in a cushioning action by virtue ofthe non-rotatable mounting of the coupling shaft 21 relative to theconnecting bracket 50 and the cushioning filler 24 so as to counteractthe movement jay in the anti-clockwise direction. In case, theconnecting plate 52 is turned about the central axis in theanti-clockwise direction so as to bring the coupling shaft 21 togethertherewith, the stop member 54 will abut against the other one of theabutment edges 521 of the connecting plate 52 by virtue of a restorationforce of the spiral spring plate 22 and the filler 24 relative to thecircumferential wall 23 so as to result in another cushioning effectsand to counteract the movement in the anti-clockwise direction. Thus,the vibrations of the front and rear wheel-carrying frame members 30, 40of the bicycle 1 (see FIG. 1) will be considerably absorbed. Since theshock-absorbing joint of this invention eliminates the need for acylinder and spring arrangement to interconnect the front and rearwheel-carrying frame members 30, 40 as taught in the prior art, andsince there is no noise generated during collision of the cushioningbumper 238 and the stop member 54 against the abutment edges 521 of theconnecting plate 52, the disadvantages that result from the use of theknown shock-absorbing joint can be avoided.

With this invention thus explained, it is apparent that numerousmodifications and variations can be made without departing from thescope and spirit of this invention. It is therefore intended that thisinvention be limited only as indicated in the appended claims.

I claim:
 1. A shock-absorbing joint adapted to interconnect a frontwheel-carrying frame member and a rear wheel-carrying frame member of abicycle, said shock-absorbing joint comprising: a tubular casing adaptedto be connected securely to one of the front and rear wheel-carryingframe members, said tubular casing confining an accommodating spacewhich defines a central axis that is disposed horizontally and thatextends in a transverse direction relative to a riding direction of thebicycle; a coupling shaft disposed in said accommodating space andextending along the central axis of said accommodating space; a spiralspring plate disposed in said accommodating space, and having aninnermost end connected to said coupling shaft and an outermost endconnected to said tubular casing, said spiral spring plate being woundabout said coupling shaft to form a series of interconnected turns ofincreasing radius; and a connecting bracket adapted to be connectedsecurely to the other one of the front and rear wheel-carrying framemembers, said tubular casing being mounted rotatably on said connectingbracket, said coupling shaft being mounted non-rotatably on saidconnecting bracket; and wherein said connecting bracket includes aconnecting plate that extends in the transverse direction and that hasleft and right ends, and left and right support plates that extendrespectively and transversely from said left and right ends of saidconnecting plate to flank opposite ends of said tubular casing, saidconnecting plate being adapted to be connected securely to the other oneof the front and rear wheel-carrying frame members, said left and rightsupport plates having said opposite ends of said tubular casing mountedrotatable thereon, and further having opposite end portions of saidcoupling shaft mounted non-rotatably thereon.
 2. The shock-absorbingjoint as defined in claim 1, wherein said spiral spring plate definesclearances between adjacent ones of said turns thereof and between aninnermost one of said turns and said coupling shaft, saidshock-absorbing joint further comprising a cushioning filler made froman elastomeric material, said filler being disposed in said tubularcasing and filling said clearances defined by said spiral spring plate.3. The shock-absorbing joint as defined in claim 1, further comprising apair of cap members, each of which has an outer portion that is mountednon-rotatably on a respective one of said left and right support plates,and an inner portion that extends into a respective one of said oppositeends of said tubular casing.
 4. The shock-absorbing joint as defined inclaim 3, wherein said left and right support plates are formed withnon-circular openings therethrough, said outer portion of each of saidcap members having a cross-section that complements said non-circularopening in the respective one of said left and right support plates toenable non-rotatable engagement of said cap members with said left andright support plates in said non-circular openings.
 5. Theshock-absorbing joint as defined in claim 3, further comprising a pairof bearing members to couple rotatably and respectively said oppositeends of said tubular casing and said inner portions of said cap members.6. The shock-absorbing joint as defined in claim 3, wherein: each ofsaid opposite end portions of said coupling shaft is formed with anon-circular cross-section along a plane transverse to the central axis;and said inner portion of each of said cap members is formed with asocket that engages non-rotatably a respective one of said end portionsof said coupling shaft.
 7. The shock-absorbing joint as defined in claim6, wherein each of said end portions of said coupling shaft is formedwith an internally threaded axial bore, said shock-absorbing jointfurther comprising a pair of screw fasteners, each of which extendsthrough a respective one of said cap members and engages said axial borein a respective one of said end portions of said coupling shaft.
 8. Theshock-absorbing joint as defined in claim 1, wherein said connectingplate is curved with respect to the central axis of said accommodatingspace, and has a pair of abutment edges that interconnect said left andright ends of said connecting plate, said tubular casing having an outercircumferential wall, a portion of which being proximate to andsurrounded by said connecting plate.
 9. The shock-absorbing joint asdefined in claim 8, further comprising a stop member mounted on saidouter circumferential wall of said tubular casing, said stop memberbeing rotatable with said tubular casing relative to said connectingbracket and being capable of abutting against one of said abutment edgesof said connecting plate to limit rotation of said tubular casingrelative to said connecting bracket in a certain direction.
 10. Theshock-absorbing joint as defined in claim 9, wherein said stop member ismade of an elastomeric material.
 11. The shock-absorbing joint asdefined in claim 10, wherein said one of said abutment edges of saidconnecting plate is formed with a notch that is registered with saidstop member on said tubular casing.
 12. The shock-absorbing joint asdefined in claim 10, further comprising a screw fastener for mountingsaid stop member on said tubular casing.
 13. The shock-absorbing jointas defined in claim 8, wherein said outermost end of said spiral springplate is formed with a threaded hole therethrough, said tubular casingbeing formed with a radial hole that is aligned with said threaded hole,said shock-absorbing joint further comprising a fastener plate disposedon said outer circumferential wall of said tubular casing, and a screwfastener extending through said fastener plate and said radial hole insaid tubular casing, and that engages said threaded hole in said spiralspring plate, thereby connecting securely said outermost end of saidspiral spring plate to said tubular casing.
 14. The shock-absorbingjoint as defined in claim 13, wherein said fastener plate has one edgeproximate to one of said abutment edges of said connecting plate andprovided with a cushioning bumper, said cushioning bumper beingrotatable with said tubular casing relative to said connecting bracketand being capable of abutting against said one of said abutment edges ofsaid connecting plate to limit rotation of said tubular casing relativeto said connecting bracket in a certain direction.
 15. Theshock-absorbing joint as defined in claim 14, wherein said cushioningbumper is made of an elastomeric material.
 16. The shock-absorbing jointas defined in claim 1, wherein said coupling shaft is formed with anaxially extending slot for engaging securely said innermost end of saidspiral spring plate.
 17. The shock-absorbing joint as defined in claim1, wherein said innermost end of said spiral spring plate is connectedsecurely to said coupling shaft.